Sarge
I am familiar with Jim Clark's 38 wadcutter. He originally used a Colt 38 Super and converted it to a 38 wadcutter. It requires some real crafty gunsmithing. He also did a 38 AMU which is a rare one.
How do you like that extra 1/2" on the Barrel ( a little additional weight) but longer sight plane?

Actually Colt made a 38 AMU Slide Kit (Clark & Giles used them) for I believe 2 years, one sold on GunBroker just recently, i was sorry I saw it after it sold.

I have a Colt 38 Super (converted to 38 Spl.) that Giles did in his 45 Shop in Odessa,Fl. I am guessing in the 60ies. The Frame is dated 1961 and Giles usually had his customers send him a new gun to do the work on.

I saw a 38 Super that Giles did (which was left as a 38 Super) just last week, with just Giles front and rear sights not his full rib, accurized trigger work etc.. I had it in my hands but passed on it can't afford everything. I contacted a friend who collects them and he bought it. That was one Giles didn't do very often.